1. Field of the Invention
The present invention relates to a supporting device for the control buttons of electronic instruments and electronic instruments adapting the same.
2. Description of the Related Art
Generally, electronic instruments such as DVD player, VCR, digital audio disk player, video disk player and the like include, at the front face of a front panel for access of recording media, a plurality of control buttons including one for selecting various functions, in accordance with their own functions.
Such control buttons are pushed rearward by a force applied from a front direction to control the contact with a tact switch installed to a main board so as to switch the mode of instruments or set a desired function.
Typically, the control buttons of the instruments are horizontally installed to a front panel from a back face thereof in such a manner that the respective knobs protrude in a frontal direction through the front panel. The tact switch is installed vertically on a board horizontally installed inside the instruments, so as to operatively touch its contact with the operation of the knob of the button. Thus, the control buttons are constructed so that a pressing force horizontally exerted to the knob is vertically transferred to the tact switch. To this end, the control button has a horizontal rectangular press portion at a lower portion of its back face, so that the press portion can be swung rearward with a horizontal force applied to closely contact with the tact switch.
Meanwhile, a control button has recently been proposed having its knob, press portion and the like formed on a single rib structure to facilitate the easy engagement with the front panel. Also, in course of the engagement with the front panel, a contact surface of the front panel and the control button would be in common so that the restricted inner space of the front panel could be effectively utilized.
FIGS. 1A and 1B are sectional views illustrating a control button installed to the front panel of a typical electronic instrument.
Referring the FIGS. 1A and 1B, a board 11 is horizontally placed in the body 10 of an electronic instrument. On the board 11, a tact switch 12 is installed which has a contact 12a that is operated with a vertical press force.
The front panel 20 is attached to the front of the body 10. The front panel 20 has an exposed outer panel 21 and a hidden inner panel 23 coupled thereto.
The control button 30 has a button rib 31 that is substantially parallel to the back face of the inner panel 23, a knob 33 extending forward from the button rib 31 that is exposed in front of the front panel 20, and a press portion 35 extending rearward from the button rib 31 to press the contact 12a of the tact switch 12.
The button rib 31 is fixedly put into a fixing boss 23a formed on the back face of the inner panel 23. Also, the button rib 31 has a deformable resilient portion 31a between a lower portion thereof supported by the fixing boss 23a and an upper portion thereof on which the knob 33 is provided. When the knob 33 is forced rearward in an arrow direction A, the upper portion of the button rib 31 is rearward and downward swung about the resilient portion 31a while the resilient portion 31a is resiliently deformed, so that the press portion 35 presses the contact 12a. 
Meanwhile, in the above construction, in order that the knob 33 is not eccentrically positioned from the center of the through-hole 20a formed in the front panel 20, a protrusion 23b is formed on the back face of the inner panel 23. Since the upper portion of the button rib 31 is supported by being in contact with the protrusion 23b, the knob 33 is constantly positioned at the center of the through-hole 20a. 
However, in such construction, the front panel 20 is fabricated as a mold product generally made of plastic materials in comparison with the body 10 of the instrument, so that it may be deformable when an external force is applied. Specifically, with recent demand for slim sized instruments, the thickness of the front panel 20 has become thinner. In this case, when the users contact the front panel 20 on the upper and lower portions, the front panel 20 is applied with a force in an arrow direction A illustrated in FIG. 1A, thus deforming the middle portion of the front panel 20. When the middle portion of the front panel 20 is deformed like this, a press force is produced so that the protrusion 23b moves the button rib 31 rearward. Accordingly, even though the users do not operate the knob 33, there is a problem in that the button rib 31 has a pressing force applied by the resilient deformation of the front panel 20, thus causing a malfunction of the tact switch 12.